1. Field of the Invention
This invention is directed to the field of medium and high voltage cables and more particularly to the grounding of the concentric neutral conductors of such cables.
2. Description of the Prior Art
The concentric neutral conductors of medium to high voltage cables are formed as wire or tape braids wrapped about the semi-conductive insulation shield of such cable. The neutral conductors are intended to provide a return circuit for load currents and to maintain the shield at ground potential to prevent injury to persons coming in contact with the cable.
Since the concentric neutral conductors are on the outside of the cable and the cable is intended to be buried in the ground, the concentric neutral conductors are attacked and destroyed by ground water, hostile elements in the environment of the cable, such as polluted ground water, corrosive acids, bases and other chemical substances present The destruction of the concentric neutral conductors thus removes the return path for the load, fault and charging currents and could cause increasing voltage potentials on the shield.
To prevent destruction of the concentric neutral conductors, an insulating or a semi-conductive jacket can be placed over the cable as well as the concentric neutral conductors. This semi-conductive jacket is relatively expensive. The requirement that the concentric neutral conductors be grounded at regular intervals is met by the semi-conductive jacket, but with the insulating jacket it is required that the cable jacket be removed and the concentric neutral conductors be to a ground point. The cable must be sealed at the interruption of the cable jacket and the ground wires protected. This is a slow and expensive process.